2015 CVT Issues

[09mlb86]

I have a 2015 RF and the transmission has been acting up for about 20k miles. It has just over 89k miles now. And it wouldn't start for my wife. It was cranking slowly like it was stuck in gear and had a P0791 code intermediate shaft speed sensor A circuit. I bought a cheap sensor off Amazon and replaced it. The check engine light went away and it started, park, neutral, and reverse work but when I put it in drive it acts like I put it in B and shifting to B doesn't change how it acts. I ordered name brand sensors and I'm going to replace both Polly sensors and the speed sensor. Any other ideas or anyone else experience this? I told it to Certified Transmission a few months ago and they said the transmission was fine but the engine was underpowered.

If you were driving with cruise control on some times it would just stop driving the car forward and hit the rev limiter. If you cancel cruise and then resume it would go back to working fine for a while. When it started doing that consistently I learned if I changed the CVT fluid it would work right for a few thousand miles but then it would start acting up again.

Also the highway fuel economy dropped from about 50mpg to down below 29 MPGs over this time.

I did 0-60 test it and it took 16.6 seconds to get to 60. My co worker has a 2018 and his took about 11.4 seconds

[Fummins]

Sounds similar to this one https://mirageforum.com/forum/showth...l=1#post159858
These cvt's are hit or miss as far as reliability goes. Dirty fluid causes all sorts of problems. The valve body's are really finiky. THey have a bunch of filters in them. I haven't really had any luck cleaning them out and having them work properly but I have had one 2015(with 233k kms) that was throwing a p0746 and would stop reving up, after dropping the pan and valve body numerous times then eventually replacing the valve body with a known good one, the car started driving fine again It now has around 480k kms and still going.

[09mlb86]

Sounds similar to this one https://mirageforum.com/forum/showth...l=1#post159858
These cvt's are hit or miss as far as reliability goes. Dirty fluid causes all sorts of problems. The valve body's are really finiky. THey have a bunch of filters in them. I haven't really had any luck cleaning them out and having them work properly but I have had one 2015(with 233k kms) that was throwing a p0746 and would stop reving up, after dropping the pan and valve body numerous times then eventually replacing the valve body with a known good one, the car started driving fine again It now has around 480k kms and still going.

Do you think the name brand sensors might help at least for now? The ones I bought before were a total of $25 from Amazon I ended up buying 3 Beck/Arnley sensors for about $300. I figured they at least made the check engine light go away and made it start and drive so maybe better sensors will make it work correctly in drive.

[Fummins]

I couldn't tell you if the sensors would work. They might just temporarily mask an underlying problem. Have you dropped the oil pan?

I should redo my last post...I'll do that here:
As for the hard cranking, I don't think that's anything to do with the transmission unless you have a something major going on like the torque convertor or oil pump piled up inside? Probably unrelated but maybe your battery cables are badly corroded or weak battery causing problems?

It acts like it's stuck in B mode and revs too high. Are you positive the fluid level is correct? I don't think I ran into one acting like that but the car in the one link I posted did throw that same P0791 code then eventually acted like it was slipping so I just replaced the entire unit.
$300 would go a long ways towards a used cvt.
Have you ever replaced any of the filters in the cvt, mainly the one on the side of the case? I had a comment on one of my vijeo's form someone that worked at Mitsu(not sure if dealer or ?) and said that Mitsubishi got irritated with the number of warranty cvt's that were replaced that just had the cartridge filter plugged and had no other damage. I don't know if that's true or if they had no visible damage but the valve body was hooped like the case was in my own cvt that I tore down here.
I'd hate to see you throw $300 at it and it not fix the problem.

[09mlb86]

I couldn't tell you if the sensors would work. They might just temporarily mask an underlying problem. Have you dropped the oil pan?

I should redo my last post...I'll do that here:
As for the hard cranking, I don't think that's anything to do with the transmission unless you have a something major going on like the torque convertor or oil pump piled up inside? Probably unrelated but maybe your battery cables are badly corroded or weak battery causing problems?

It acts like it's stuck in B mode and revs too high. Are you positive the fluid level is correct? I don't think I ran into one acting like that but the car in the one link I posted did throw that same P0791 code then eventually acted like it was slipping so I just replaced the entire unit.
$300 would go a long ways towards a used cvt.
Have you ever replaced any of the filters in the cvt, mainly the one on the side of the case? I had a comment on one of my vijeo's form someone that worked at Mitsu(not sure if dealer or ?) and said that Mitsubishi got irritated with the number of warranty cvt's that were replaced that just had the cartridge filter plugged and had no other damage. I don't know if that's true or if they had no visible damage but the valve body was hooped like the case was in my own cvt that I tore down here.
I'd hate to see you throw $300 at it and it not fix the problem.

It has a new interstate battery less than 6 months old. The no start and check engine light went away with the new cheap sensors but then it acted like it was in B even when it was in D and shifting to B didn't change how it acted. I have not changed the filter yet was going to do it if it.made it to 100k miles. It was a repo car and I don't think the CVT fluid was changed the first 69k miles of its life. It was black like my tor oil when I drained it out the first time. During the hard start it felt like it was stuck in gear or like the starter was going out. When I read the code there was only one and replacing the sensor made it start easy again. In the past 20k miles I have flushed it with about 12 quarts of CVT fluid as that usually made it work correctly again and without an error code I had no where to look. That's a helpful video of the teardown. Thanks for uploading it

[7milesout]

I'm not a CVT guy. But you will be money FAR AHEAD to follow Fummins' advice. And to me, the symptoms you describe sound like multiple root causes. And it sounds like you were right to replace the battery. Gonna need one anyway, not money wasted.

Since the battery is taken care of, from this point, the rest of the symptoms DO sound like they originate in the valve body. Fummins knows how to source those local to you. He's posted how to do that, probably in the threads linked before. Course there's a matter of luck with that too. Maybe it won't be next door, but should be fairly local. And especially since you talk about the fluid being dark, sounds like (at least) the valve body is a gonner.

Now, I've not pulled down a valve body. Because a Chrysler 727 doesn't get busted unless you run it dry. But I did pull the pan off, replaced the filter, set the ... holy crap, what was that called, some kind of belt tensions from 1st to 2nd, and 2nd to 3rd, eyeballed the valve body ... seems like I might have replaced something simple on the valve body (besides the filter). But the valve body on that "looked" like it would be fairly easy to remove / replace. Messy, but doable. I have no idea really if the valve body on your CVT vehicles would be as easy as that.

At the very least, assuming it is just a valvebody, source a valve body (for cheap), and take it to a private mechanic and just say, "please remove the pan and valve body, slap this valve body up in there, slap this CVT fluid in when you have the pan back on (hand him some bottles), then give me the old valve body when your done." Can't be all that expensive, might cost less than the $300 your considering for the sensors (course I don't know about that). It would be money well spent. Then race your coworker, should be close.